How do I design a low-ΔT syndrome solution for chilled water plants?

Low-ΔT syndrome occurs when chilled water returns to the plant at a lower temperature than designed (e.g., 48°F instead of 54°F), reducing overall plant capacity and forcing additional chillers online prematurely. The root causes are typically oversized control valves operating near their seats, coils with inadequate surface area or fouling, and poor balancing causing overflow in near-coil circuits. Solutions include installing pressure-independent control valves (PICVs) or Belimo Energy Valves on every cooling coil to limit flow to design, implementing coil ΔT monitoring with automated alarms when ΔT falls below 60% of design, and using 2-way control valves with variable-speed secondary pumps instead of 3-way bypass valves that short-circuit chilled water. Per ASHRAE guidance, a plant with a ΔT of less than 10°F is considered to have low-ΔT syndrome and may benefit from a chilled water reset strategy that raises supply temperature during low-load conditions.